This invention relates generally to an automatic transmission and more particularly to a controller for a direct coupling clutch. In an automatic transmission equipped with a torque converter comprising a pump, a turbine and a stator, it is known to economize on fuel by directly connecting the pump to the output shaft of the turbine by means of a direct-coupling clutch. This is done when the automatic transmission is shifted to the high speed range in order to improve the efficiency of power transmission. In this transmission comprising a direct-coupling clutch, when the direct-coupling clutch is engaged, frequently while the automatic transmission has shifted to a range other than the high speed range, overheating of the working fluid of the torque converter, or engine stall is liable to occur. Accordingly, highly reliable performance of the direct-coupling clutch operating circuit is essential to the automatic transmission.
What is needed is an automatic transmission which is automatically, directly or indirectly, coupled to satisfy operating conditions of the vehicle and protect the transmission and torque converter.